Challenges to computing buoyancy-driven flows in the containment system of LWRs

An advanced model for evaluating the temporal and spatial distribution of non-condensable gases, including the simulation of buoyancy-driven flows, in a multi-compartment containment system of a LWR is reviewed. The model employs an analogy technique with electrical networks to determine the convection flows among the containment compartments and evaluates, inside a single node, the profile of the vertical concentrations of steam and non-condensable gases. The proposed model has been used to investigate the natural circulation phenomena occurring in the HDR E11.2 and in the FIPLOC-F2 test. The experiment performed on the HDR facility is fundamental for the analyses of the hydrogen distribution inside a multi-compartment system, while the FIPLOC-F2 test was focused on the natural circulation phenomena during a typical severe accident sequence. The simulation of these two tests allowed to get relevant information relating to the knowledge of the buoyancy driven flows in the containment system of the actual and of the advanced generation of LWRs. 12 refs., 8 figs